The production of devices capable of emitting light through chemical means is well known in the art. Lightsticks, for example, are taught in U.S. Pat. No. 3,539,794 while other configurations have also been the subject of many U.S. Pat. Nos. e.g. 3,749,620; 3,808,414; 3,893,938. Additional recent patents include U.S. Pat. No. 4,635,166 and U.S. Pat. No. 4,814,949.
The device shown in FIG. 2 of U.S. Pat. No. 4,814,949 is one over which the devices of the present invention are an improvement. Such a device comprises a first polymeric sheet having a shaped cavity therein, sealed around its periphery to a second polymeric sheet and the cavity contains (1) an absorbent article produced from a polyolefin, or a polyester or glass fibers and being of substantially the same shape as the cavity and (2) a sealed receptacle containing a first liquid component of a chemiluminescent light composition and wherein there is also present, outside said sealed receptacle, a second liquid component of a chemiluminescent light composition, said absorbent article conforming to several preferred features. The devices of this type have achieved widespread commercial acceptance, but they have one drawback, and that is a tendency to distort or inflate during storage and/or use because they are totally sealed and gas-tight.
The present invention provides improved low profile (flat), flexible devices of the above-mentioned, totally-sealed type in which a liquid component is substantially immobilized within the internal cavity. Even though gases are generated during storage or use there is no longer observed unwanted distortion or inflation because a novel venting means is now provided in the form of an annular passage formed adjacent to the peripheral seal of the device. One end of the annular passage is open to the atmosphere. The annular passage may be empty or contain a means to entrap residual liquid while it allows gases to pass freely through to the atmosphere. A preferred embodiment of the invention comprises an oliophobic material within the annular passage in the form of a porous foam (open cell) or fibrous structure. The invention has particular utility in chemical light producing devices which are assembled with liquid chemicals premixed at temperatures below ambient so as to slow or stop the light producing reaction. The light producing chemicals may be absorbed in fibrous or foam pad structures. Such devices may be stored at suitable low temperatures until use later when exposure to ambient temperature warming causes the reaction to begin and generate light. Another embodiment useful to chemical light devices is to add an adhesive tab or overlay seal over the vent hole to atmosphere during storage so as to protect against unwanted gas or vapor from the atmosphere reacting with chemical components within the device. The overlay or adhesive seal may be removed during operation of the device to eliminate the restriction to gas flow.